The present invention relates to a solubilizing agent and a hydrosol composition obtained by using the solubilizing agent, and more particularly, to a solubilizing agent capable of solubilizing an oil-soluble material such as colorants, perfumes, vitamins, anti-oxidants, preservatives, germicides or fats and oils in an aqueous solvent, and a hydrosol composition containing the oil-soluble material solubilized in the aqueous solvent.
Conventionally, in the fields of cosmetics, deodorants, bath agents, aromatizing agents, deodorizers, food, medicines or the like, various products exhibiting a liquid state at ordinary temperature have been prepared by solubilizing oil-soluble materials such as colorants, vitamins, anti-oxidants, preservatives, germicides or fats and oils in an aqueous solvent by using an emulsifier. However, in the case where these oil-soluble materials are solubilized in an aqueous solvent by using such an emulsifier, there have been caused the problem that the oil-soluble materials are separated from the aqueous solvent during the preparation of these products or during storage or transportation after the preparation thereof.
In order to solve such problems concerning oil/water separation, there have been conventionally proposed methods of adding polyhydric alcohols, surfactants or the like as a solubilizing agent to the aqueous solvent. Some of these methods have been already put into practice. Typical examples of conventionally proposed solubilizing agents include surfactants such as lecithin, polyoxyethylene sorbitan monooleate (nonionic surfactant), hardened castor oil ethylene oxide adducts, sucrose fatty acid esters or the like.
It is known that polyglycerol fatty acid esters (hereinafter occasionally referred to merely as "POGE") are safe emulsifiers usable for food, cosmetics or the like. In addition, there have been proposed solubilizing agents using the POGE. However, when an oil-soluble material is solubilized in an aqueous solvent by using the conventionally proposed POGE solubilizing agents, it has been required to further add other additives such as polyhydric alcohols. Further, it is necessary to use unsaturated fatty acids having a low stability independent to change with time as main constituting fatty acids of the POGE, thereby adversely affecting perfuming of cosmetics, distribution or storage of the goods or the like.
Also, in the preparation of the conventional solubilizing agents, there arises such a problem that in order to surely solubilize the oil-soluble substance in the aqueous solvent, it is necessary to use an emulsifier, a high-pressure homogenizer or the like capable of applying a strong shear force to a raw composition upon solubilizing operation. For these reasons, it has been demanded to develop solubilizing agents which are capable of solubilizing an oil-soluble material in an aqueous solvent by simple operation and maintaining the obtained solubilized products with a good stability for a long period of time, and do not adversely affect perfuming when applied to cosmetics.
On the aim for solving these problems, there have been proposed novel POGEs (Japanese Patent Applications Laid-open (KOKAI) Nos. 7-308560(1995), 7-100355(1995), 9-238619(1998) or the like). However, since these POGEs are insufficient in solubilizing property, it has been required to use a large amount of the POGE relative to that of an oil-soluble component to be solubilized.
As a result of the present inventor's earnest studies for solving the above-mentioned problems, it has been found that by using polyglycerol having a high degree of polymerization as a base polymer of polyglycerol fatty acid ester, it becomes possible to extremely readily solubilize an oil-soluble material in an aqueous solvent. The present invention has been attained by the finding.